Partial oxidation and similar operations involve contacting hydrocarbons with oxygen under conditions that form a gaseous product stream having a desired composition of gaseous components. However, past experience has shown that the gaseous product stream often contains solid particulate byproducts such as soot, especially when the gaseous product stream is produced under conditions that are intended to retain a significant component of one or more hydrocarbon components by not fully reacting or combusting them. These solid particulate byproducts may also be present when the partial oxidation reactions take place at low temperatures. That is, if the reaction conditions do not achieve complete oxidation of all oxidizable components that are present, or if the reactor temperature is low, then some unoxidized matter that is present in the product stream would be expected to be in the solid phase. Alternately the reaction conditions could be such that the cracking temperature of the feed is exceeded without adequate conversion of the feed to a gaseous product stream. The solid particulate byproduct is referred to generally as “soot” and may comprise elemental carbon, and/or carbon-containing hydrocarbons. The presence of this material in the product stream from the partial oxidation operation is often undesirable. However, previous efforts to lower the amount of this material that is in the product stream have required sacrificing yield, or increasing the usage of reactants such as oxygen, which are approaches that have drawbacks.